Itami never found his feet in WWE so the news that he's decided to leave the company is not that surprising. After coming in hot to NXT, he was plagued by a series of injuries that kept him from the main event spot he really deserved an opportunity at. His English was also said to be an issue, and hindered his ability to get himself over on the mic to some extent.
At any rate, WWE's loss will almost certainly be indie wrestling fans' gain, as we will soon get to see KENTA kicking people's heads off their shoulders again.